The semiconductor industry continues to present a need for the development of new dielectric materials with a low dielectric constant (k). In integrated chips or other microelectronic structures, dielectric material is typically in contact with metal interconnects, which provide conductive channels. Diffusion of metals such as copper (Cu) from interconnects into adjacent dielectric material can lead to the degradation of the electrical properties of the dielectric.
A metal barrier can be applied on a dielectric material to prevent diffusion, as shown in FIG. 1. Layers of tantalum nitride 9 and tantalum 7 are deposited over patterned dielectric 3 disposed on substrate 1. The layers 9 and 7 form a metal barrier against diffusion of Cu from the subsequently applied interconnect 2 into the patterned dielectric 3.
A self-forming metal barrier shown in FIG. 2 can also be used to prevent Cu diffusion from an interconnect into an adjacent dielectric material. A seed layer 4 of Cu—Mn (copper-manganese) alloy is deposited over patterned dielectric 3 disposed on a substrate 1, followed by deposition of a Cu interconnect 2. On heating the structure, a non-Cu metal component Mn in the Cu—Mn alloy segregates to the interface between the dielectric 3 and the interconnect 2. The Mn then reacts with the dielectric to form a barrier layer 5.